This invention relates to thin film and hybrid integrated circuits, and in particular to a conduction system for interconnecting elements in said circuits.
Thin film and hybrid integrated circuits presently enjoy extensive use in a wide variety of applications, for example, filter circuits and memories for switching and transmission systems. The most widely used metal interconnection system used for such applications is a titanium-palladium-gold multilayer structure. The gold layer provides the major current-carrying load while also serving as a good bonding layer. While such a system has performed satisfactorily, great quantitites of gold are required. Typically, the gold layer is approximately 50,000 A thick and must be formed over a substantial area of the interconnect pattern. With the rising cost of gold, the cost of producing such circuits can become excessive.
Finding a replacement for such a system is an exceedingly difficult task. The system must not only provide good conduction and adherence to the substrate, but must also be compatible with the various processing sequences necessary for circuit fabrication, such as thermo-compression bonding, soldering, resistor and capacitor fabrication and stabilization, annealing, etc. The various components of the system must also be compatible, i.e., nonreactive, with each other.
It is therefore a primary object of the invention to provide a metal interconnection system which is less expensive than the presently used system and at the same time is compatible with the myriad processing requirements of thin film and hybrid circuits.